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Rustproofing is the prevention or delay of
rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH ...
ing of
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
and
steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
objects, or the permanent
protection Protection is any measure taken to guard a thing against damage caused by outside forces. Protection can be provided to physical objects, including organisms, to systems, and to intangible things like civil and political rights. Although th ...
against
corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
. Typically, the protection is achieved by a process of surface finishing or treatment. Depending on mechanical wear or environmental conditions, the
degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradatio ...
may not be stopped completely, unless the process is periodically repeated. The term is particularly used in the
automobile industry The automotive industry comprises a wide range of companies and organizations involved in the design, development, manufacturing, marketing, and selling of motor vehicles. It is one of the world's largest industries by revenue (from 16 % such ...
.


Vehicle rustproofing


Factory

In the factory, car bodies are protected with special chemical formulations. Typically,
phosphate conversion coating Phosphate conversion coating is a chemical treatment applied to steel parts that creates a thin adhering layer of iron, zinc, or manganese phosphates, to achieve corrosion resistance, lubrication, or as a foundation for subsequent coatings or pai ...
s were used. Some firms galvanized part or all of their car bodies before the
primer Primer may refer to: Arts, entertainment, and media Films * ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth * ''Primer'' (video), a documentary about the funk band Living Colour Literature * Primer (textbook), a t ...
coat of paint was applied. If a car is body-on-frame, then the frame (chassis) must also be rustproofed. In traditional automotive manufacturing of the early- and mid-20th century, paint was the final part of the rustproofing barrier between the body shell and the atmosphere, except on the underside. On the underside, an
underseal {{Unreferenced, date=December 2009 On vehicles Underseal (often called undercoating in the U.S.) is a thick resilient coating applied to the underbody or chassis of an automobile to protect against impact damage from small stones, which would rapi ...
rubberized or PVC-based coating was often sprayed on. These products will be breached eventually and can lead to unseen corrosion that spreads underneath the underseal. Old 1960s and 1970s rubberized underseal can become brittle on older cars and is particularly liable to this. The first electrodeposition
primer Primer may refer to: Arts, entertainment, and media Films * ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth * ''Primer'' (video), a documentary about the funk band Living Colour Literature * Primer (textbook), a t ...
was developed in the 1950s, but were found to be impractical for widespread use. Revised
cathodic A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
automotive electrocoat primer systems were introduced in the 1970s that markedly reduced the problem of corrosion that had been experienced by a vast number of automobiles in the first seven decades of automobile manufacturing. Termed e-coat, "electrocoat automotive primers are applied by totally submerging the assembled car body in a large tank that contains the waterborne e-coat, and the coating is applied through cathodic electrodeposition. This assures nearly 100% coverage of all metal surfaces by the primer. The coating chemistry is waterborne enamel based on
epoxy Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...
, an
aminoalcohol In organic chemistry, alkanolamines are organic compounds that contain both hydroxyl () and amino (, , and ) functional groups on an alkane backbone. The term alkanolamine is a broad class term that is sometimes used as a subclassification. Meth ...
adduct An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
, and blocked
isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...
, which all
crosslink In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
on baking to form an epoxy-urethane resin system. E-coat resin technology, combined with the excellent coverage provided by electrodeposition, provides one of the more effective coatings for protecting steel from corrosion. For modern automobile manufacturing after the 1990s, nearly all cars use e-coat technology as base foundation for their corrosion protection coating system.


Aftermarket

Aftermarket kits are available to apply rustproofing compounds both to external surfaces and inside enclosed sections, for example sills/rocker panels (see
monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
), through either existing or specially drilled holes. The compounds are usually wax-based and can be applied by aerosol can, brush, low pressure pump up spray, or compressor fed spray gun. An alternative for sills/rocker panels is to block drain holes and simply fill them up with wax and then drain most of it out (the excess can be stored and reused), leaving a complete coating inside. Anti-rust wax like
phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
based rust killers/neutralizers can also be painted on already rusted areas. Loose or thick rust must be removed before anti-rust wax like Waxoyl or a similar product is used. Structural rust (affecting structural components which must withstand considerable forces) should be cut back to sound metal and new metal welded in, or the affected part should be completely replaced. Wax may not penetrate spot-welded seams or thick rust effectively. A thinner (less viscous) mineral-oil-based anti-rust product followed by anti-rust wax can be more effective. Application is easier in hot weather rather than cold because even when pre-heated, the products are viscous and don't flow and penetrate well on cold metal. Aftermarket "underseals" can also be applied. They are particularly useful in high-impact areas like wheel arches. There are two types - drying and non-drying. The hardening and drying products are also known as "Shutz" and "Anti Stone Chip" with similar potential problems to the original factory underseals. These are available in black, white, grey and red colors and can be overpainted. These are best used for the area below the bumpers on cars that have painted metal body work in that location, rather than modern plastic deep bumpers. The
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...
based products do not dry and harden, so they cannot become brittle, like the confusingly named "Underbody Seal with added Waxoyl" made by Hammerite, which can be supplied in a Shutz type cartridge labelled "Shutz" for use with a Shutz compressor fed gun. Mercedes bodyshops use a similar product supplied by Mercedes-Benz. There are many manufacturers of similar products at varying prices, these are regularly group tested and reviewed in the classic car magazine press. The non drying types contain anti-rust chemicals similar to those in anti-rust waxes. Petroleum-based rust-inhibitors provide several benefits, including the ability to creep over metal, covering missed areas. Additionally, a petroleum, solvent-free rust inhibitor remains on the metal surface, sealing it from rust-accelerating water and oxygen. Other benefits of petroleum-based rust protection include the self-healing properties that come naturally to oils, which helps undercoatings to resist abrasion caused by road sand and other debris. The disadvantage of using a petroleum-based coating is the film left over on surfaces, rendering these products too messy for top side exterior application, and unsafe in areas where it can be slipped on. They also cannot be painted. There are aftermarket electronic "rustproofing" technologies claimed to prevent corrosion by "pushing" electrons into the car body, to limit the combination of oxygen and iron to form rust. The loss of electrons in paint is also claimed to be the cause of “paint oxidisation” and the electronic system is also supposed to protect the paint. However, there is no peer reviewed scientific testing and validation supporting the use of these devices and corrosion control professionals find they do not work. Baboian, R., "State of the Art in Automobile Cathodic Protection," SAE Technical Paper 912270, 1991, doi:10.4271/912270


Rate of corrosion

The rate at which vehicles corrode is dependent upon: *Local climate and use of ice-melting chemicals (
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
) upon the roads *Atmospheric pollution, such as acid rain or
salt spray Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantiti ...
, which can cause paint damage *Quality, thickness, and composition of metal used, often an alloy of mild steel *Improper use of some dissimilar metals, which can accelerate the rusting of steel bodywork through
electrolytic corrosion Galvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. A sim ...
*Design of "rust traps" (nooks and crannies that collect road dirt and water) *Particular process of rustproofing used *Plastic/under-seal protection on the car underside *Exposure to salt water, which strips off the protective paint and also causes rust much more quickly than ordinary rain water would


Rustproof alloys

Stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...
, also known as "inox steel" does not stain, corrode, or rust as easily as ordinary steel.
Pierre Berthier Pierre Berthier (; 3 July 1782, Nemours, Seine-et-Marne – 24 August 1861) was a French geologist and mining engineer. Pierre Berthier was born in Nemours. After studying at the École Polytechnique, he went to the École des Mines, where he b ...
, a Frenchman, was the first to notice the rust-resistant properties of mixing chromium with alloys in 1821, which led to new metal treating and metallurgy processes, and eventually the creation of usable stainless steel. DeLorean cars had a fiberglass body structure with a steel backbone chassis, along with external brushed stainless-steel body panels. Some cars have been made from aluminum, which may be more corrosion resistant than steel when exposed to water, but not to salt or certain other chemicals.


See also

*
Corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
*
Corrosion engineering Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to mana ...
*
Hot-dip galvanizing Hot-dip galvanization is a form of galvanization. It is the process of coating iron and steel with zinc, which alloys with the surface of the base metal when immersing the metal in a bath of molten zinc at a temperature of around . When expose ...
*
Tinning Tinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. The term is also widely used for the different process of coating a metal with solder before soldering. It is most ...
*
Iron pillar of Delhi The iron pillar of Delhi is a structure high with a diameter that was constructed by Chandragupta II (reigned c. 375–415 AD), and now stands in the Qutb complex at Mehrauli in Delhi, India.Finbarr Barry Flood, 2003"Pillar, palimpsets, and pr ...
* Cathodic Protection for Vehicles *
Cosmoline Cosmoline is the genericized trademark for a common class of brown, wax-like petroleum-based corrosion inhibitors, typically conforming to United States Military Standard MIL-C-11796C Class 3. They are viscous when freshly applied, have a sligh ...
*
Corrosion inhibitor In chemistry, a corrosion inhibitor or anti-corrosive is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The effectiveness ...


References

{{commons category, Rust Vehicle technology Corrosion prevention Materials science